Power amplifiers typically have been designed to operate within limited or narrow frequency bands because of technical challenges associated with broadband amplifier design. If it is desired to communicate within a large number of frequency bands, a correspondingly large number of product lines, each designed for one of the frequency bands, must therefore be offered. The large number of product lines for the different frequency bands increases the design, manufacture and inventory cost, along with the size, weight and complexity of the associated electronic components.
There have been recent efforts to develop broadband power amplifiers which would be useful in broadband communications systems such as the Joint Tactical Radio System (JTRS). To accommodate this increased bandwidth, which may for example range from 200 MHz to 2000 MHz, the matching networks within the amplifier circuitry must be designed to minimize insertion loss and maximize return loss over the wider frequency band. This may require additional electrical components because of a lower matching network quality factor, and the additional components may cause the structure size to increase, which may result in prohibitively large amplifier structures.
One of the components in an amplifier structure is a transformer placed between a power amplifier and other electronic components. The impedance of an amplifier output signal may be on the order of 1 ohm, yet must be matched to an impedance load of 50 ohms when the amplifier output is processed by other electronic components. Known transformers intended for use with broadband communication systems are prohibitively large and cannot reasonably be used in portable communications systems.
It is therefore an object of the invention to reduce the physical size of a broadband power amplifier structure.
It is also an object of the invention to reduce the physical size of a transformer used in a broadband power amplifier.
A feature of the invention is a transformer having a substrate with a variable height.
An advantage of the invention is a reduction in size of a broadband transformer.